Method of manufacture of rp(o) cl2 from rp(o)(or)2 and socl2



United StatestPatent O METHOD or MANUFACTURE OF fRP()Cl FROM muouon AND soci Thomas P. Dawson, Bel Air, Md., and Jack W. Armstrong, Concord, Califl, assignors to the United States of America as-represented by the Secretary of the Army No Drawing. Application April 26, 1955 Serial No. 504,127

4 Claims. (Cl. 260-643) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to us of any royalty thereon.

The object of this invention is to produce an alkyl phosphonic chloride. More specifically, the object is to produce an alkyl phosphonic dichloride by reacting a corresponding phosphonate with thionyl chloride.

The preparation of alkyl phosphonic dichlorides in high yields has heretofore been somewhat diflicult. Several methods have been used with varying results. The following equations illustrate some of these prior art reactions:

ll CHg-P-OR 2P0]: 2011 O I CHr-1 -C1 2POC1; 2301 (where R is an alkyl group) In this reaction, POCl remains with the reaction product and separation is difficult.

In the present process, the phosphonate is reacted with thionyl chloride as follows:

i i R-P=O +s001= RP=O 801 R01 where R represents alkyl groups.

This reaction is readily obtained under ordinary conditions by the reaction of 30% molecular excess of SOCl and refluxing for 3 hours at 75-80 C. When using 110% molecular excess of SOCl a higher yield of the t'. monochloride was obtained but no appreciable quantity of the dichloride resulted.

To prepare the dichloride in accordance with the following equation:

(DR 31 RP=O 2s001, R-P=O 2801 21101 requires a higher temperature. Thus at 130 to 200 C. in an electrically heated column a 65 to yield is secured without column fractionation.

Example.-l.0 mol SOCl is placed in a flask and is heated to a refluxing temperature of 78 C. The flask is fitted with an 18" electrically heated column containing a packing of V4" Berl saddles. 0.25 mol diisopropyl methylphosphonate is added at a definite rate through the column which is heated to a reaction temperature of 130 to200 C.

The phosphonate is completely chlorinated to the corresponding dichloride in accordance with the following equation:

H CH2 L CH: (ill H/CHs CH; =0 28001: CHaP=O 280: 25

/CH: 1 1 CH: Iii: CH:

The by-products, S0 and isopropyl chloride escape from the top of the column and are. collected in traps cooled in a Dry Ice-acetone mixture. Thus the preparation of the dichloride and its separation from the by-products of the reaction is accomplished in one convenient step. Yields of 80% or better are obtained of a very pure product, methylphosphonic dichloride, which was once distilled and analyzed with the following results:

M. P.32.4-32.6 (M. P. of pure material 32.7 C.) Cl-53.76; 53.36 (calculated) P-23.1 1; 23.31 (calculated) The alkyl phosphonic dichlorides have many uses, one of the most common being that of an intermediate in the following reaction:

The final product is known as isopropyl methylphosphonofiuoridate. It has well known toxic properties as a war gas.

We claim:

1. A process of producing an alkylphosphonic dichloride which comprises refluxing thionyl chloride at a temperature of substantially 78 C., passing vapors of said thionyl chloride up a column heated to a temperature in the range to 200 C., and feeding a lower dialkyl alkylphosphonate down said column.

2. A process as defined in claim 1 wherein said phosphonate is a lower dialkyl methylphosphonate.

Patented Aug. 12, 1958 3 3i A process in' ac'cdrdar'ice-with claim 1 wherein the byproducts of S0; and alkyl chloride arecollected in cooled traps after passing up through the column.

7 4. A process of producing methylphosphonic dichloride w'la'iclrcom-prises refluxing thionylchlorideat a temperature of substantially 78 C.,' passing vapors of said thionyl chloride" upa column heatedto a temperature References Cited in the file of this patent UNITED STATES PATENTS Hagemeyer-et al Aug. 28, 1951 Coover et al. Mar. 24,1953 

1. A PROCESS OF PRODUCING AN ALKYLPHOSPHONIC DICHLORIDE WHICH COMPRISES REFLUXING THIONYL CHLORIDE AT A TEMPERATURE OF SUBSTANTIALLY 78*C., PASSING VAPORS OF SAID THIONYL CHLORIDE UP A COLUMN HEATED TO A TEMPERATURE IN THE RANGE 130* TO 200*C., AND FEEDING A LOWER DIALKYL ALKYLPHOSPHONATE DOWN SAID COLUMN. 